The overall research goal is to clarify and define the role of iodine metabolism in the development of breast dysplasia and carcinoma. The specific objective is to evaluate the efficacy of technics for determining breast iodine concentration as a means for early diagnosis of human breast cancer. In addition, the study includes the relationship of estrogen therapy, thyroid disease, gestational history, and breast-feeding status as they relate to iodine metabolism and the pathogenesis of mammary gland malignancy. Technics for breast iodine uptake studies, as well as breast imaging and X-ray intensification, are being developed and evaluated. These are being compared with existing methods of xeromammography and clinical breast examinations. For the coming year, the major thrusts will be towards: 1) increasing our available data on iodine uptakes, 2) evaluating the variables defined in light of breast pathology, 3) determining serum concentration of iodine for comparison, 4) further evaluation of follow-up data as they become available, and 5) developing interpretation of the pertechnetate breast image.